Seventy-seven children and adolescents with drug-resistant epilepsies received vigabatrin as add-on therapy for a median of 18 months (range 4-36 months) at a dose of 50 mg/kg/day divided in two doses; patients with spasms were given a maximum dose of 100 mg/kg/day. In 23 patients (29.9%), seizure frequency decreased by 50-100% and in 12 patients (15.6%) by 25-50%. The number of seizures remained unchanged in 34 patients (44.1%) and increased in seven (9.1%). Vigabatrin was most effective in cryptogenic and symptomatic partial seizures (39% and 43%, respectively), and in infantile spasms (25%). Adverse events occurred in 20 patients (26%), though they were generally mild and transient, suggesting that vigabatrin is well tolerated.